9) Departure from ancestral environments can create unanticipated problems. Species are adapted to their long-term past environments, not necessarily to their present environments. In new environments, old adaptations sometimes go spectacularly awry. As one example, the diet of many children today includes a much higher ratio of omega-6 to omega-3 fatty acids than the ancestral human diet, which may adversely affect neural and cognitive development. Other examples include physical activity and touching. Schoolchildren are commonly required to sit still for extended periods, and touching is sometimes prohibited as a guard against sexual harassment. These practices have a surface logic in today's society, but they ignore the fact that physical movement and touching among trusted associates were always part of the human ancestral environment. Children who are deprived of movement and touching become hormonally stressed, which may compromise their ability to learn. Many of the problems that schools and children experience today may be unintended consequences of educational environments that are strikingly different from ancestral conditions.10) Some skills are acquired less spontaneously than others and require more deliberate effort. Some skills, such as walking and talking, have been essential for so many generations that we have become genetically prepared to learn them at an early age. Virtually all children practice those skills naturally in the course of their daily lives, more or less automatically. By contrast, other skills are unique to a given culture, and these may often require more conscious effort. Every culture, including every hunter-gatherer culture, has such unique skills. For example, different hunter-gatherer cultures have different, often extraordinarily sophisticated ways of tracking game depending on the terrain and the kinds of game they hunt. They also have different sets of tools—such as blowpipes, bows and arrows, or snares for hunting—which must be crafted to perfection and require great skill to use. Reading and mathematics are examples of modern culturally valued skills that we are not specifically adapted, genetically, to acquire. Children will be naturally motivated to acquire such skills only to the degree that they observe them in successful role models or find such practice to be immediately useful and enjoyable. Even so, some amount of non-spontaneous practice and explicit instruction may be necessary for students to master these skills.